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Let's say an action Fibonnaci takes 5 minutes to complete. If Fibonacci is called twice in quick succession, does the second call need to wait 5 minutes for the first call to complete, or do they run concurrently?
I think it depends upon how you code the node that provides the ActionServer. On the client side you can start a new action with ActionClient.send_goal_async which will return a future. When that future completes, the result will tell you if the action was accepted. Your server side code can decide to accept a new action or not.
I have used a MultiThreadedExecutor and can successfully handle new action requests whilst an existing callback is running (running a while loop to navigate a robot to a goal pose). Not used a RentrantCallbackGroup, but that is not to say you shouldn't.
I can try switching to single threaded executor and see what happens...
@SmallJoeMan Actually would you be open to switching to a single threaded executor to see what happens?
All rclpy examples use a MultiThreadedExecutor, so I think it is a requirement: examples_rclpy_minimal_action_server
It's correct that you must use a MultiThreadedExecutor for action servers in rclpy. I think this is because we chose to use the executor to process the user-provided "execute" function. In contrast, rclcpp's implementation of the action server leaves it up to the user to handle separate threads when executing goals, and so a single threaded executor is fine.
It's is probably worth considering a refactor in rclpy such that any executor is compatible.
Asked: 2020-12-09 14:37:36 -0500
Seen: 641 times
Last updated: Dec 09 '20
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